Hundreds of thousands of Nigerians fleeing Islamist militants are searching for sanctuary, say government and international relief officials, the latest fallout from Boko Haram's campaign to seize the northeast of Africa's most populous country.

Local authorities said Tuesday that in a fresh exodus from violence, hundreds of people continued to flee Gwoza, a town of about 50,000 near Nigeria's remote border with Cameroon that suspected Boko Haram fighters overran last Wednesday. Boko Haram has made the surrounding Borno...